Dynon ? Lightspeed tacho wiring?

The Dynon EMS120 harness comes with two simple 24AWG wires for the right- and left RPM signal. The Lightspeed manual however calls for a shielded wire with the shield to be connected to the Lightspeed control box as well as to the tacho ground?
Does anybody have experience with this wiring? Would it be OK to just use the 24AWG wire from the Dynon harness and connect the pin of the Lightspeed, that should be connected to the shield, to aircraft ground?

As usual, thanks in advance
Regards, Tonny.

no shield

I didn't use shielded wire to the dynon (FD180) and the tach works fine.

Noise?

Grover,
And no noise in the Headset?

Thanks for your reply.
Regards, Tonny

To piggyback on that question, my LSE unit must be an older model -- it has two shielded wires coming out of the input plug, one for power and the other for ground. However, the schematic that came with it shows just ONE shielded wire for both power and ground, and the second wire for electronic tach.

I took apart the plug to see exactly what pins the wires were attached to and, indeed, one wire is for power and the other ground. Pin 6, the one for RPM, had no wire attached to it at all. So, I soldered a 14 ga wire to it and put the plug back together.

If that's how I'm supposed to get tach info to my Dynon unit, then WHY wasn't a wire already soldered to pin 6 in the first place?

Any and all help greatly appreciated!

I'm in a similar boat. Just ran my engine yesterday, and no RPM signal comes to the D180 from the Lightspeed III.

Connected the Right Mag wire from the Dynon to pin 6 on the input connector of the Lightspeed. Also verified that using the P-lead + 30k ohm resistor resulted in correct RPM to either L or R input of the EFIS (with the Lightspeed disconnected).

I had a note from Dynon's forum that I may not be able to have both P-lead and Lightspeed connected at the same time; a software issue causes problems when the two input leads are set to different number of pulses per revolution. But, that doesn't explain why I get no signal from the LS when it is the sole hookup.

Only other thing I can think of is that I did NOT hook up LS Input pin #13 (grnd for signal shield). It SHOULD be redundant as both boxes share a common ground, but....???

I just received an e-mail from Klaus Savier saying that running a wire from pins 6 & 13 (the shield ground pin) is the right thing to do. I'm assuming that the shielding is for noise suppression and that it's not needed at the EMS end.

However, since I also have one mag and one LSE unit, I'm now wondering if I even want to bother with hooking up the RPM from the LSE unit? If the Dynon won't recognize it, I'll just stick with the P-lead from the mag and use my ears when I check the LSE side during "mag" check.

N8RV said:

I just received an e-mail from Klaus Savier saying that running a wire from pins 6 & 13 (the shield ground pin) is the right thing to do. I'm assuming that the shielding is for noise suppression and that it's not needed at the EMS end.

However, since I also have one mag and one LSE unit, I'm now wondering if I even want to bother with hooking up the RPM from the LSE unit? If the Dynon won't recognize it, I'll just stick with the P-lead from the mag and use my ears when I check the LSE side during "mag" check.

Click to expand...

That's where I'm at, although it seems ridiculous that a 10v pulse would not be enough to trigger the Dynon. It is especially annoying because SOME people have gotten it to work. Until someone comes up with a fix, like you I'll have to keep it disconnected.

Ok, after a couple of emails Klaus provided some insight which might explain our dilemma. The issue is that some versions of the Plasma III only put out a 5v signal instead of a 10v signal as is indicated on the diagram - if you didn't read the fine print (note #6) you would never know it. Klaus' email below, bold is mine.

Thanks Klaus!

Bill,

_____________________________________________________________

Bill,

On the Label under the serial number is a "Version" line. It also is engraved on the underside and written on the packing list you received if you still have it.
You might have an A version which will not work with the Dynon but can be modified here.

Input Connector Diagram
See note 6 on the above link.

Regards,
Klaus Savier
Light Speed Engineering, LLC
P.O. Box 549
416 E. Santa Maria St., #15
Santa Paula, CA 93060 USA
[email protected]
Tel: (805) 933-3299 Fax: (805) 525-0199

Click to expand...

For the mag side, does anyone have a picture of how you wired the resistor in place? The instructions say to place it as close to the P-lead as possible. However, those things are so fragile-looking that there HAS to be an acceptable way to wire a resistor in-line securely enough that it won't break from the vibration.

How have others done it?

Don't have a photo handy, but what I did is the following:

Near the end of the tach lead from the Dynon harness to the Mag switch I installed the resistor in-line, then added 1 1/2" of wire with a #8 loop terminator. I then connected that to the same terminal on the mag switch that goes to ground (not to the mag), so that if the switch is turned off you will get no RPM reading.

Works like a champ, and if I ever manage to get the Lightspeed tach reading then I will know absolutely the RPM when I do mag drops (because only the working "mag" will be providing pulses).

I think I'm following you. On the Slick mag, there's a ground screw that the braided shield attaches to, per Van's wiring harness instructions. That screw is grounded through the mag case. So, instead of attaching the Dynon wire to the P-lead, attach it to the mag ground screw instead? I guess I wouldn't have thought that the RPM pulse would get to the Dynon that way ...

And just solder & heat shrink over the resistor splice for reinforcement? (this is all new to me, sorry -- of course, so is EVERYTHING about building an airplane!)

Thanks.

N8RV said:

I think I'm following you. On the Slick mag, there's a ground screw that the braided shield attaches to, per Van's wiring harness instructions. That screw is grounded through the mag case. So, instead of attaching to the P-lead, attach it to the mag ground? I guess I wouldn't have thought that the RPM pulse would get to the Dynon that way ...

And just solder & heat shrink over the resistor splice for reinforcement? (this is all new to me, sorry -- of course, so is EVERYTHING about building an airplane!)

Thanks.

Click to expand...

Ok, you've made me think about what I did - I just tested it Sunday...

The P-lead exits the mag and runs to the cockpit and attaches to the mag switch (seperate 2-position toggle in my setup; some folks use a key switch). When the switch is in the "off" position it is really closed (e.g. lets the P-lead electrons flow through to the grounding wire). What this means is, I lied to you!



I must have attached the pickup to the terminal with the P-lead attached, otherwise I would never get RPM when the mag is "hot."

And I honestly don't know what will happen when the switch is closed - it may still get the signal, but the ground may draw enough signal off that it no longer senses it. I don't think I actually looked at the RPM with the mag switched off, because I was just so happy to get a reading at all....